Currently, digital communication has revolutionized telephone networks. There are legal organizations for monitoring telephonic communications wherever there is a chance of suspect of any terror or for any other illegal operations. A Lawful interception (LI) is the legally sanctioned official access to private communications, such as telephone calls or e-mail messages. In general, LI is a security process in which a network operator or service provider gives law enforcement officials access to the communications of private individuals or organizations.
In the discipline of Lawful Interception, it is important to distinguish and know between Network Access and Network Services since the two are somewhat different by convention. Network Access is typically managed by the Network Access Provider (AP), who's infrastructure often (but now always) relies on that of the Network Operator (NWO), such as the incumbent telecom operator, local cable TV service, or wireless services operator. Network Services mentioned here are be E-mail, chat, WIFI etc. In the context of lawful interception, Lawful enforcement Agencies (LEA) often must interact with both Network Access and Network Services to intercept target data. The target meant here was the intercepted person.
Conventional methods of LEA interception and monitoring of call by suspect (LI target) comprises typical interception and monitoring of call by a LEA. The method comprises LEA interface (LEAI) activates interception for a subscriber (LI target). This activates interception for all calls involving the LI target until the LI is deactivated by the LEAI. Next, call initiation and interception method in which a call involving the LI target is initiated with the LI target being the calling or the called user in the call. While setting up the call involving the LI target subscriber, the Media gate controller (MGC)/Softswitch initiates interception of the call. The MGC passes signaling information, and initiates transfer of media information from the MGW to LEA Interface (via LIG). The LEA monitors current state of the call using information received. Next, performing Dual Tone Multi-Frequency (DTMF) reporting and false release trigger, in which the calling or the called user may perform some DTMF activity to trigger a false call release event. The DTMF activity is captured by the Media Gateway (MGW) and reported to the Anti-Fraud Control System Interface in the MGC through Media Gateway Interface. The MGC reports the DTMF activity to the Anti-Fraud Control system (or sub-system). Also, the MGC receives a (false) release trigger due to the DTMF activity by calling or called user. Thereafter, call and interception termination is performed by the MGC. The MGC performs the call termination based on the (false) release trigger received to release all the resources for the call on the signaling plane. The MGC performs call interception termination based on this (false) release trigger. The MGC informs LEA through LEA interface that the call is released (over HI2 signaling interface as CC Close message), and the media information transmission through LEAI is stopped.
In this method, it is clear that the media path between the calling and called user is still active even after the call-release in the signaling plane, since the release trigger was a false one intended to terminate the connection on the signaling plane only, while the two users involved in the call will continue their conversation. Since the MGC/Soft switch terminates the interception of the call based on the false release trigger, the LI target subscriber can continue communication without being monitored by the LEA as the MGW stops sending media information to the LEA through LEAI.
Available mechanism fails to ensure that the target interception continues with LEA till the actual call disconnection happens in the network. The key limitation are determination of actual call status in case of a potentially fraudulent call and taking action on the call based on preference of LEA in order for uninterrupted tracking of the LI target.
There exists a need to have a mechanism to identify actual status of a potentially fraudulent call on real-time basis and take appropriate measures for uninterrupted tracking of the LI target by LEA.